One of the most common eye disorders, dry eye disease, causes irritation or discomfort, and can decrease functional vision, sometimes causing a dramatic deterioration in the quality of life. About five million Americans over age 50 suffer from moderate-to-severe dry eyes, and tens of millions more have mild or episodic manifestations of the disease, at a cost of more than $50 billion.

In terms of treatment, there are several drops and drugs that can help. We spend hundreds of millions of dollars on things like artificial tears, but currently there is no therapy available to actually fix the problem. If drugs don't work, doctors can try plugging up the outflow tear ducts, but that can cause complications, such as plugs migrating and eroding into the face, requiring surgical removal. Alternatively, surgeons can just cauterize or stitch up the ducts in the first place.

There has to be a better way.

What about prevention? Dry eyes can be caused by LASIK surgery, affecting about 20-40% of patients six months after the operation. With a million LASIK procedures performed annually, that's a lot of people, and sometimes the long-term symptoms can be severe and disabling.

There's a long list of drugs that can cause it, including antihistamines, decongestants, nearly all the antidepressants, anticonvulsants, antipsychotics, anti-Parkinson's drugs, beta-blockers, and hormone replacement therapy, as well as a few herbal preparations.

In the developing world, vitamin A deficiency can start out as dry eyes and then progress to becoming the leading cause of preventable childhood blindness. Vitamin A deficiency is almost never seen in the developed world, unless you do it intentionally. There was a report in the 1960s of a guy who deliberately ate a vitamin A-deficient diet, living off of bread and lime juice for five years, and his eyes developed vascularization and ulceration of the cornea, which you can see (if you dare) in my Treating Dry Eye Disease with Diet: Just Add Water?video.That was better than what happened to an unfortunate woman who was the member of a cult and tried to live off of brown rice and herbal tea: Her eyes literally melted and collapsed.

There are also a couple case reports of autistic children who refused to eat anything but French fries or menus exclusively comprised of bacon, blueberry muffins, and Kool-Aid, and became vitamin A deficient. A case in the Bronx was written up as vegan diet and vitamin A deficiency, but it had nothing to do with his vegan diet--the kid refused to eat vegetables, consuming only potato chips, puffed rice cereal with non-fortified soymilk, and juice drinks. "His parents lacked particular skill in overcoming the child's tendency to avoid fruits and vegetables."

A plant-based diet may actually be the best thing for patients with dry eye disease, those who wear contact lenses, and those who wish to maximize their tear secretions. People with dry eyes should be advised to lower protein, total fat, and cholesterol intake, and do the following:

We know dehydration can cause a dry mouth, but could dehydration cause dry eyes? It may seem kind of obvious, but evidently it was never studied until recently. Is the answer to just drink more water? We know that those suffering from dry eye are comparatively dehydrated, so researchers figured that tear secretion decreases with progressive dehydration just like saliva secretion decreases and gives us a dry mouth. And indeed, as one gets more and more dehydrated, their urine concentrates and so does the tear fluid. But one can reverse that with rehydration, raising the exciting prospect that improving whole-body hydration by getting people to drink more water might bring relief for those with dry eyes. The researchers recommend eight cups of water a day for women and ten cups a day for men.

One of the most common eye disorders, dry eye disease, causes irritation or discomfort, and can decrease functional vision, sometimes causing a dramatic deterioration in the quality of life. About five million Americans over age 50 suffer from moderate-to-severe dry eyes, and tens of millions more have mild or episodic manifestations of the disease, at a cost of more than $50 billion.

In terms of treatment, there are several drops and drugs that can help. We spend hundreds of millions of dollars on things like artificial tears, but currently there is no therapy available to actually fix the problem. If drugs don't work, doctors can try plugging up the outflow tear ducts, but that can cause complications, such as plugs migrating and eroding into the face, requiring surgical removal. Alternatively, surgeons can just cauterize or stitch up the ducts in the first place.

There has to be a better way.

What about prevention? Dry eyes can be caused by LASIK surgery, affecting about 20-40% of patients six months after the operation. With a million LASIK procedures performed annually, that's a lot of people, and sometimes the long-term symptoms can be severe and disabling.

There's a long list of drugs that can cause it, including antihistamines, decongestants, nearly all the antidepressants, anticonvulsants, antipsychotics, anti-Parkinson's drugs, beta-blockers, and hormone replacement therapy, as well as a few herbal preparations.

In the developing world, vitamin A deficiency can start out as dry eyes and then progress to becoming the leading cause of preventable childhood blindness. Vitamin A deficiency is almost never seen in the developed world, unless you do it intentionally. There was a report in the 1960s of a guy who deliberately ate a vitamin A-deficient diet, living off of bread and lime juice for five years, and his eyes developed vascularization and ulceration of the cornea, which you can see (if you dare) in my Treating Dry Eye Disease with Diet: Just Add Water?video.That was better than what happened to an unfortunate woman who was the member of a cult and tried to live off of brown rice and herbal tea: Her eyes literally melted and collapsed.

There are also a couple case reports of autistic children who refused to eat anything but French fries or menus exclusively comprised of bacon, blueberry muffins, and Kool-Aid, and became vitamin A deficient. A case in the Bronx was written up as vegan diet and vitamin A deficiency, but it had nothing to do with his vegan diet--the kid refused to eat vegetables, consuming only potato chips, puffed rice cereal with non-fortified soymilk, and juice drinks. "His parents lacked particular skill in overcoming the child's tendency to avoid fruits and vegetables."

A plant-based diet may actually be the best thing for patients with dry eye disease, those who wear contact lenses, and those who wish to maximize their tear secretions. People with dry eyes should be advised to lower protein, total fat, and cholesterol intake, and do the following:

We know dehydration can cause a dry mouth, but could dehydration cause dry eyes? It may seem kind of obvious, but evidently it was never studied until recently. Is the answer to just drink more water? We know that those suffering from dry eye are comparatively dehydrated, so researchers figured that tear secretion decreases with progressive dehydration just like saliva secretion decreases and gives us a dry mouth. And indeed, as one gets more and more dehydrated, their urine concentrates and so does the tear fluid. But one can reverse that with rehydration, raising the exciting prospect that improving whole-body hydration by getting people to drink more water might bring relief for those with dry eyes. The researchers recommend eight cups of water a day for women and ten cups a day for men.

Over the counter antacids are probably the most important source for human aluminum exposure in terms of dose. For example, Maalox, taken as directed, can exceed the daily safety limit more than 100-fold, and nowhere on the label does it say to not take it with acidic beverages such as fruit juice. Washing an antacid down with orange juice can increase aluminum absorption 8-fold, and citric acid-the acid found naturally concentrated in lemon and limes--is even worse.

Just as sour fruits can enhance the absorption of iron (a good thing), the same mechanism they may enhance the absorption of aluminum (a bad thing). This raises the question of what happens when one adds lemon juice to tea? Previously, I concluded that the amount of aluminum in tea is not a problem for most people because it's not very absorbable (See Is There Too Much Aluminum in Tea?). What if we add lemon? Researchers publishing in the journal Food and Chemical Toxicologyfound no difference between tea with lemon, tea without lemon, or no tea at all in terms of the amount of aluminum in the bloodstream, suggesting that tea drinking does not significantly contribute to aluminum getting inside the body.

The researchers used black tea, green tea, white tea, oolong tea, but what about the "red zinger" herbal tea, hibiscus? The reason hibiscus tea is called "sour tea" is because it has natural acids in it like citric acid. Might these acids boost the absorption of any hibiscus's aluminum? While a greater percentage of aluminum gets from the hibiscus into the tea water than from the other teas, there's less aluminum overall.

The real question is whether the aluminum then gets from the tea water into our bodies. We don't have that data, so to be on the safe side we should assume the worst: that hibiscus tea aluminum, unlike green and black tea aluminum, is completely absorbable. In that case, based on this data and the World Health Organization weekly safety limit, we may not want to drink more than 15 cups of hibiscus tea a day, (based on someone who's about 150 pounds). If you have a 75 pound 10-year-old, a half-gallon a day may theoretically be too much. Recent, more extensive testing highlighted in my video, How Much Hibiscus Tea is Too Much?, suggests that levels may reach level twice as high. Therefore, to be safe, no more than about two quarts a day for adults, or one quart a day for kids or pregnant women. Hibiscus tea should be completely avoided by infants under six months--who should only be getting breast milk--as well as kids with kidney failure, who can't efficiently excrete it.

There is also a concern about the impressive manganese level in hibiscus tea. Manganese is an essential trace mineral, a vital component of some of our most important antioxidant enzymes, but we probably only need about two to five milligrams a day. Four cups of hibiscus tea can have as much as 17 milligrams, with an average of about ten. Is that a problem?

One study from the University of Wisconsin found that women given 15 milligrams of manganese a day for four months, saw, if anything, an improvement in their anti-inflammatory, anti-oxidant enzyme activity. Another study using 20 milligrams a day similarly showed no adverse short-term effects, and importantly showed that the retention of dietary manganese is regulated. Our bodies aren't stupid; if we take in too much manganese, we decrease the absorption and increases the excretion. Even though tea drinkers may get ten times the manganese load (10 or 20 milligrams a day) the levels in their blood are essentially identical. There is little evidence that dietary manganese poses a risk.

These studies were conducted with regular tea, though, so we don't know about the absorption from hibiscus. To err on the side of caution we should probably not routinely exceed the reference dose of ten milligrams per day, or about a quart a day for adults and a half-quart for a 75 pound child.

I've actually changed my consumption. Given the benefits of the stuff, I was using it as a substitute for drinking water, drinking around two quarts a day. I was also blending the hibiscus petals in, not throwing them away, effectively doubling the aluminum content, and increasing manganese concentrations by about 30%. So given this data I've cut back to no more than a quart of filtered hibiscus tea a day.

The lactic acid that makes yogurt tangy is the same lactic acid that builds up in our muscles when we exercise strenuously. Instead of bacteria fermenting the sugar in milk to make energy for themselves, our muscles ferment sugar in our diet to produce energy to contract. If, like when we’re sprinting, lactic acid builds up in our muscles faster than it can be removed we can end up with a burning sensation in our muscles, forcing us to stop.

Now if we train, we can increase the number of blood vessels in our muscles and clear out the lactate faster. For example, when researchers took some overweight sedentary women and started them on an aerobic training program of running and walking, at the end of three months, their lactate levels during exercise dropped 17%. But those on the same program who drank two cups of orange juice a day dropped their levels 27%. They did the same exercise program, but the citrus group experienced a significant decrease in blood lactate concentration, indicating an improvement in physical performance with less muscle fatigue.

I don’t recommend drinking juice, though, because we’re losing all that wonderful fiber that slows the rate of fruit sugar absorption into our system. In my video, Reducing Muscle Fatigue with Citrus, we can see the blood sugar spike one might expect after drinking Coca-Cola. Compare that to the spike we see with orange juice? No difference. However, if we eat the same quantity of sugar in the form of orange slices we experience a significantly smaller spike in blood sugar.

So the whole fruit is nearly always better than fruit juice. Now this is not to say OJ isn’t better than coke. OJ has those citrus phytonutrients like hesperidin, which may be why the women’s triglycerides didn’t go up even though they were drinking two cups of fruit juice every day. Hesperidin may actually help lower our digestion of fats, but once we get up to three cups a day, we really can start bumping our triglycerides.

The burning sensation during strenuous exercise may be related to the build-up of lactic acid in our muscles, but that’s different than the delayed onset muscle soreness that occurs in the days following a bout of extreme physical activity. That’s thought to be due to inflammation caused by muscle cell damage, little micro-tears in the muscle. If it’s an inflammatory reaction then might anti-inflammatory phytonutrients help? Find out in my video Reducing Muscle Soreness with Berries.

In 1936, Albert Szent-Györgyi, who won the Nobel Prize for discovering vitamin C, described a vitamin “P,” which we now know encompasses a class of thousands of phytonutrients called flavonoids. Some, like quercitin, are widespread in plant-based foods. We can tell something is widespread in the plant kingdom when one can even find it in iceberg lettuce!

Others, however, are only found in specific plant families. For example, hesperidin is found primarily in citrus fruits. This may be one of the reasons that, out of all the different types of fruit that have been looked at, citrus may cut our risk of stroke the most.

The citrus phytonutrient hesperidin increases blood flow. Using a machine called a Doppler fluximeter (sounds like something from Back to the Future) one can measure blood flow through the skin using a laser beam. When researchers give people the amount of hesperidin found in two cups of orange juice, blood flow goes up. It works even better when they gave them the orange juice itself, so there’s other beneficial stuff besides just the hesperidin in citrus.

For example, if we measure the changes in genetic expression, orange juice consumption induces changes in the expression of 3000 of our genes, whereas hesperidin alone only modulated the expression of about 2000. Still, the fact that nearly 2000 stretches of our DNA expressed differently because we consumed just one of the thousands of phytonutrients in plants is pretty mind-blowing.

These changes in blood flow are not just in theory. Researchers took volunteers with cold sensitivity (cold hands and feet), put them in an air-conditioned room and measured the temperature of their fingertips after drinking a placebo drink (like orange Kool-Aid) versus drinks with two doses of actual citrus phytonutrients. In the Kool-Aid group, their fingers got colder and colder, dropping nearly nine degrees Fahrenheit. The fingers of those consuming low or high doses of citrus didn’t get nearly as cold because their blood flow remained steady. In my video, Keeping Your Hands Warm with Citrus, we can see the laser test of the subject's blood flow. When we’re exposed to cold temperatures our body starts to clamp off peripheral blood flow to keep our core warm, but if we eat a bunch of oranges before we go skiing our risk of frostbite may go down since we’re keeping up our blood flow to our fingers and toes.

They even took these poor women and plunged their hands into some chilly water, and their finger temperature rebounded faster towards normal in the citrus group, demonstrating that citrus phytonutrients not only keep our extremities warmer but may also warm us back up faster.

But don't forget, don't brush your teeth immediately after consuming citrus. We have to make sure to rinse our mouth with water and wait 30 minutes before brushing to protect our tooth enamel (see Plant-Based Diets: Dental Health).

Because different families of fruits and vegetables can have entirely different phytonutrient profiles, variety is important. See, for example: